JPH11302094A - Method for manufacturing compound semiconductor single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a compound semiconductor single crystal, which can effectively prevent twins from being generated in a diameter-increased portion of a crystal and can manufacture a compound semiconductor single crystal with a higher yield. I do. SOLUTION: A cylindrical crucible 1 having an inverted conical diameter-increased portion A on a lower end side and a seed crystal S installation portion 2 at the center of the bottom of the diameter-increased portion is used. The seed crystal is set in the seed crystal setting part, the compound semiconductor raw material 3 and the encapsulant 4 are charged into the crucible, and the crucible is sealed in an airtight container. The raw material and the sealant are placed in and heated and melted by heating means,
When growing the compound semiconductor single crystal by gradually cooling the obtained raw material melt from the lower side and solidifying it from the seed crystal upward, the crystal growth rate in the diameter-increased portion of the crucible was increased by 20 mm. / Hr or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a compound semiconductor single crystal, and more particularly to vertical gradient freezing (hereinafter, referred to as "cooling") in which a material melt of a compound semiconductor such as InP is cooled to grow a single crystal in the vertical direction. The present invention relates to a technique that is useful when applied to a VGF (VGF) method or a vertical Bridgeman (VB) method.

[0002]

2. Description of the Related Art Conventionally, generally, for example, GaAs or InP
For industrial production of such compound semiconductor single crystal ingots, a liquid-sealed Czochralski (LEC) method or a horizontal Bridgman (HB) method is used.

The LEC method has the advantages that a wafer having a large diameter and a circular cross section can be obtained, and a high-purity crystal can be easily obtained because a liquid sealant (B ₂ O ₃ ) is used. On the other hand, since the temperature gradient in the crystal growth direction is large, the transition density (EPD) in the crystal is disadvantageously increased. Therefore, when an electronic device such as an FET (field effect transistor) is manufactured using the crystal, a problem arises in that electrical characteristics are deteriorated due to crystal defects.

[0004] On the other hand, the HB method has an advantage that a crystal having a low transition density can be obtained due to a small temperature gradient in a crystal growth direction. On the other hand, the HB method has a large diameter because a raw material melt is solidified in a crucible (boat). However, there is a disadvantage in that it is difficult to form the wafer, and furthermore, only a wafer having a shape (for example, a kamaboko shape) depending on the crucible shape can be obtained.

[0005] Therefore, vertical gradient freezing (VG) has been proposed as a method for producing a single crystal which has the advantages of the HB method and the LEC method while compensating for the disadvantages of each.
F) method and vertical Bridgman (VB) method were developed.

According to these single crystal production methods, a circular wafer can be obtained by using a cylindrical crucible with a bottom, and the temperature gradient in the crystal growth direction is small, so that the dislocation density of the grown crystal can be easily reduced. Can be achieved.

However, the above-mentioned VGF method and VB method are
It is susceptible to the effects of minute temperature changes in the reactor, or the irregularities on the inner wall of the crucible, and foreign matter attached to the crucible. The probability of generation of crystals is high, which is the main cause of lowering the yield of single crystal production.

[0008] Among these drawbacks, the influence of temperature fluctuations in the reactor has been solved by recent advances in temperature control technology. Also, regarding the generation of polycrystal on the inner wall of the crucible, the liquid sealant (B
_The use of ₂ O ₃ ) has made it possible to prevent this.

[0009] However, no effective preventive measures have yet been proposed for the formation of twins in the crystal-increased portion from the crystal growth start point to the straight body portion.

When a compound semiconductor single crystal having a zinc blende structure such as GaAs or InP is grown using a seed crystal, the inclination angle of the diameter-increased portion from the seed crystal to the straight body and the generation of twins are generated. It has been found that probabilities are closely related.

That is, when growing a crystal having a (100) orientation, a (111) facet surface appears in the diameter-increased portion, and twins are generated from the facet surface. This phenomenon has also been confirmed in experiments performed by the present inventors. According to the experiments performed by the present inventors, all twins were generated along the facet plane in a crystal in which twins were generated.

Since the (111) facet plane makes an angle of 54.7 ° with the (100) direction, it is generally (11) facet.
1) In order to prevent the appearance of the facet surface, the inclination angle of the enlarged diameter portion of the crucible is set to (90 ° -54.7 °), that is, 35.
3 ° or less.

However, when the inclination angle of the diameter-increased portion is reduced, the diameter-increased portion of the grown crystal also becomes longer, which causes a problem that the yield of the wafer is reduced and the productivity is deteriorated.

In addition, the inclination angle of the diameter increasing portion of the crucible is set to 40 °.
There is also a report that crystal growth should be performed at an angle of about 50 ° (Semiconductor Research Vol. 35, P4, etc.). However, when the present inventors conducted additional tests, the inclination angle of the diameter-increased portion was 30 ° to 50 °.
It has been found that within the range, the generation of twins cannot be sufficiently suppressed.

Therefore, the present applicant (Japan Energy Co., Ltd.) has proposed that when a compound semiconductor single crystal is manufactured by the VGF method or the VB method, the crucible bottom surface is gradually lowered toward the center thereof. On the other hand, a single crystal manufacturing method has been proposed in which a crucible inclined at a predetermined angle of 80 ° or more and less than 90 ° is used to suppress generation of twins (Japanese Patent Application No. 9-119069).

In this manufacturing method, since the bottom surface of the crucible is substantially flat, there is substantially no diameter-increased portion when moving from the seed crystal to the straight body portion, and the diameter-increased portion in which twinning is likely to occur. Thus, the crystal growth time was extremely short, and a significant reduction in the probability of twinning could be expected.

[0017]

However, twin crystals are more likely to be generated in physical properties of InP than GaAs. Therefore, when crystal growth is performed by the VGF method or the VB method, the diameter of the InP is also increased by the above manufacturing method. The generation of twins in the part could not be sufficiently suppressed.

Therefore, regarding the production of InP single crystal,
A method of using a seed crystal having a diameter similar to that of a crystal grown in the VGF method or the VB method and physically eliminating a diameter-increasing portion from the seed crystal to a straight body portion so as to prevent twins from being generated. Proposed.

However, the above method requires a seed crystal having a diameter as large as the crystal to be grown.
There is a problem that the seed crystal portion is wasted much, the production cost is high, and it is not practical for industrial production.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and effectively prevents twins from being generated in a diameter-increased portion of a crystal, thereby achieving a higher yield of a compound semiconductor single crystal, particularly a compound semiconductor single crystal. It is an object of the present invention to provide a method for manufacturing a compound semiconductor single crystal capable of manufacturing a compound semiconductor single crystal that easily causes twinning like InP.

[0021]

In order to achieve the above object, a method for producing a compound semiconductor single crystal according to the present invention has an inverted conical diameter-increased portion at the lower end side, and the diameter of the diameter-increased portion is increased. Using a bottomed cylindrical crucible having a seed crystal installation part in the center of the bottom, a seed crystal is installed in the seed crystal installation part of the crucible, and a raw material and a sealant of the compound semiconductor are put into the crucible, and the After sealing the crucible in an airtight container, the airtight container is placed in a vertical heating furnace, and the raw material and the sealant are heated and melted by a heating means, and the obtained raw material melt is gradually cooled from below. When growing a single crystal of a compound semiconductor by cooling and solidifying upward from the seed crystal, the crystal is grown at a crystal growth rate of 20 mm / hr or more in the diameter-increased portion of the crucible. It is.

It is preferable that the inverted conical diameter-increased portion of the crucible has a predetermined inclination angle of 40 ° or more and less than 90 ° with respect to a normal line at the center of the bottom, more preferably 60 ° or more. Less than 90 °, particularly preferably 80 ° or more and less than 90 °.

Further, at the time of crystal growth, the temperature gradient in the crystal growth direction at least in the diameter-increased portion of the crucible is set to 1 to 1
Control may be performed so as to be 0 ° C./cm.

In the following, the present inventors outline the contents of study and the progress of the research up to the present invention.

First, the inventor of the present invention has described that the crystal is grown using a crucible having a substantially flat bottom shape so as to grow the crystal without forming as much as possible a diameter-increased portion having a high probability of twinning. For the proposal, we examined the optimal crystal growth conditions in the crystal diameter increasing part.

Generally, it is considered that the solid-liquid interface at the time of crystal growth tends to become a single crystal when the solid phase is convex, and it is therefore desirable that the crystal growth rate be as low as possible. I have. However, according to the results of experiments performed by the present inventors, even when the growth rate of the crystal is reduced, the state of the solid-liquid interface of the crystal-increased portion is not significantly improved, and the generation of twins is effectively suppressed. I couldn't do that.

As other measures for improving the solid-liquid interface, a method of appropriately changing the holding material of the crucible and a method of forcibly cooling the seed crystal portion have been proposed. According to the experiments, the formation of twins could not be reliably suppressed by any of the methods.

Therefore, the present inventors have proposed that GGF by the VGF method be used.
From the results obtained in the aAs single crystal growth experiment, it can be seen at the position where twins are generated in the crucible and at the crystal-increased portion (1).
11) Study and consider the relationship between facet patterns, (111)
It was found that the facet pattern was related to twinning.

That is, in the GaAs single crystal grown by the VGF method, when the facet pattern is close to a square, no twinning occurs at all, whereas an asymmetrical shape in which only the facets in one direction are elongated. In the case of facet patterns, twins were often observed.

The occurrence of such an asymmetric facet pattern indicates that the solidification of the melt in the diameter-increasing portion does not proceed uniformly in four directions but proceeds rapidly in one direction.
It is sufficiently conceivable that the growth state of such facets affects the generation of twins.

Based on the above considerations, the present inventors believe that in order to surely suppress the generation of twins, it is necessary to have crystal growth conditions under which facet growth proceeds with good symmetry. As a result of repeated studies and studies, it has come to be convinced that increasing the crystal growth rate to a predetermined value or more is effective for growing facets with symmetry.

Conventionally, the VGF method has a small temperature gradient in the vicinity of the solid-liquid interface, and therefore slightly varies depending on the thermal conductivity of the crystal to be grown.

The inventors of the present invention have determined that the growth rate of the diameter-increased portion of InP having physical properties in which twins are easily generated can be increased to 5 mm / hr, 10 mm, regardless of the crystal growth rate as described above.
mm / hr, 20 mm / hr, and 50 mm / hr, the crystal growth was attempted.
At m / hr, twins were generated in the region from the seed crystal to the diameter-increased portion, and an InP single crystal without twins was successfully obtained for the first time at a growth rate of the diameter-increased portion of 50 mm / hr.

However, the growth rate of the diameter-increased portion is 20 mm / hr.
In this case, the twins appeared only slightly at the ends, and a high-quality InP single crystal could be obtained in almost all of the straight body of the crystal.

Based on these results, the growth rate conditions for industrially obtaining a single crystal such as InP with good yield were determined, and the crystal growth rate of at least the diameter-increased portion (shoulder) was found to be:
20 mm / hr or more, preferably 30 mm / hr or more,
More preferably 40 mm / hr or more, most preferably 5 mm / hr or more.
The inventors have concluded that it is desirable to be 0 mm / hr or more, and have completed the present invention based on the above findings.

According to the method of manufacturing a compound semiconductor single crystal according to the present invention, it is possible to effectively prevent twins from being generated in a crystal diameter increasing portion, and to obtain a compound semiconductor single crystal with a high yield. In particular, it becomes possible to efficiently manufacture a compound semiconductor single crystal, such as InP, which easily causes twinning at a low cost.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As an example of an embodiment of the present invention, a case where an InP single crystal is manufactured by applying the method of manufacturing a compound semiconductor single crystal according to the present invention will be described with reference to FIGS. Will be explained.

FIG. 1 is a cross-sectional view showing an example of a crucible and peripheral equipment applied to the method for producing a compound semiconductor single crystal according to the present invention, FIG. 2 is a schematic explanatory view showing a diameter increasing portion of the crucible, and FIG. 1 is a schematic diagram of a crystal growth furnace applied when the present invention is applied to a VGF method.

In FIG. 1, reference numeral 1 denotes a PBN crucible, on the bottom of which a bottomed cylindrical seed crystal mounting portion 2 is formed.

The diameter-increased portion A corresponding to the bottom of the crucible 1 has an inverted conical shape, and the diameter-increased portion A is a normal line N at the center of the bottom.
Is formed so as to have an inclination angle of α (α = 40 ° or more and less than 90 °).

Then, the In crystal is set in the seed crystal setting portion 2 of the crucible 1.
A seed crystal S of P is put, and a polycrystalline raw material 3 of InP and a sealant (B ₂ O ₃ ) 4 are put into the main body of the crucible 1. Next, the crucible 1 containing the crucible susceptor 6 and the raw material 3 is placed below the inner container 5 made of quartz. In addition, a thermocouple 7 for measuring the temperature of the seed crystal is provided in the vicinity of the seed crystal installation part 2 of the crucible susceptor 6. Subsequently, a quartz lid 8 is fitted onto the upper part of the inner container 5 to seal the inner container 5.

Next, the inner container 5 set as described above is supported on the lower shaft 12 at a predetermined position of a cylindrical multi-stage graphite heater 11 in a high-pressure vessel 10 as a vertical heating furnace, as shown in FIG. It is installed. A hot zone 13 and a hot zone upper cover 14 made of a heat insulating material are provided outside the heater 11.

When the installation of the inner container 5 in the high-pressure vessel 10 is completed, heating by the cylindrical multi-stage graphite heater 11 is started while applying a predetermined pressure, and the InP polycrystalline raw material 3 is heated.
And the sealant (B ₂ O ₃ ) 4 are melted. At this time, each output of the multi-stage heater 11 is adjusted to maintain a predetermined temperature gradient such that the temperature gradually increases from the seed crystal S side toward the upper part of the raw material melt. Then, the raw material melt in the crucible 1 is gradually cooled from below to a temperature below the melting point to grow an InP single crystal upward.

Here, the temperature gradient at the time of cooling is at least the temperature gradient in the diameter-increased portion A of the crucible 1, that is, from the solid-liquid interface between the seed crystal S at the crystal growth starting point and the raw material melt, to the straight body portion of the crystal. It is desirable that the temperature gradient in the region before the growth of the crystal is started is 1 ° C./cm to 10 ° C./cm, and the crystal growth rate is 20 mm / hr or more.

This makes it possible to effectively suppress the generation of twins in the diameter-increased portion of the InP crystal.

Therefore, an InP single crystal can be obtained with a high yield, and the manufacturing cost of the InP single crystal can be suppressed.

In the above embodiment, the case where an InP single crystal is grown by the VGF method has been described. However, the present invention is not limited to this, and the present invention can be applied to the VB method. The present invention can also be applied to the case of manufacturing a compound semiconductor.

[0048]

EXAMPLES Hereinafter, examples of the method for producing a compound semiconductor single crystal according to the present invention will be described to clarify features of the present invention.

The present invention is not limited by the following embodiments.

In the above embodiment, a PBN crucible having a diameter of about 4 inches and a thickness of 1 mm was used as the crucible 1. In addition, the angle α of the diameter-increased portion A of the crucible 1 in FIG.

Then, In is placed in the seed crystal setting portion 2 of the crucible 1.
A seed crystal S composed of a P single crystal was charged, and about 5 kg of InP polycrystal 3 as a raw material and an appropriate amount of B ₂ O ₃ as a sealant 4 were further charged into the crucible 1.

Subsequently, the crucible susceptor 6 is placed under the inner vessel 5 made of quartz, and the crucible 1 containing the raw material is placed thereon as described above. Thereafter, the upper part of the inner vessel 5 is covered with a quartz lid. 8 and the inner container 5 is sealed. In addition, a thermocouple 7 for measuring the temperature of the seed crystal is provided in the vicinity of the seed crystal installation part 2 of the crucible susceptor 6.

Next, as shown in FIG. 3, the inner container 5 set as described above is installed at a predetermined position of the cylindrical multi-stage graphite heater 11 in the high-pressure vessel 10 while being supported by the lower shaft 12.

When installation of the inner container 5 in the high-pressure vessel 10 is completed, heating by the tubular multi-stage graphite heater 11 is started while applying a predetermined pressure (for example, 45 atm), and the upper end of the seed crystal S and the raw material 3 Is 1080 ° C. to 106 ° C.
The crucible 1 was heated to a temperature of 2 ° C. to melt the polycrystalline raw material 3 of InP and the sealant (B ₂ O ₃ ) 4.

At this time, each output of the multistage heater 11 is adjusted to maintain a predetermined temperature gradient such that the temperature gradually increases from the seed crystal S side toward the upper part of the raw material melt. And
The raw material melt in the crucible 1 is gradually cooled from below to a temperature below the melting point to grow an InP single crystal upward.

Here, the temperature gradient at the time of cooling is at least the temperature gradient at the diameter-increased portion A of the crucible 1, that is, from the solid-liquid interface between the seed crystal S at the crystal growth start point and the raw material melt, to the straight body of the crystal. The temperature gradient in the region up to the start of growth was 1 ° C./cm to 10 ° C./cm.

The set temperature in the high-pressure vessel 10 is adjusted so that the crystal growth rate from the seeding position to the straight body 10 mm through the diameter-increasing portion A is 50 mm / hr or more, and the growth rate thereafter is 1 mm / hr. The temperature was lowered to perform crystal growth.

Thereafter, the entire inside of the high-pressure vessel 10 is kept at 100 ° C.
/ H cooling at a rate of cooling down to near room temperature,
The grown crystal was taken out of the high-pressure vessel 10.

The obtained grown crystal was an InP single crystal having a diameter of about 4 inches and a total length of about 12 cm. When its crystallinity was examined, no twin or polycrystal was generated.

Further, when this InP single crystal was cut and the transition density (EPD) was examined, the transition density was 10,000 cm ^-2 or less at any position of the crystal.

In addition, as a result of conducting several experiments of crystal growth in the same manner, an InP single crystal free of twinning can be obtained in all the experiments. It has been confirmed that it is extremely effective in suppressing odor.

As described above, according to the single crystal manufacturing method of the present embodiment, an InP single crystal can be obtained with a high yield, and the manufacturing cost of the InP single crystal can be reduced.

In the above embodiment, the case where an InP single crystal is grown has been described. However, the present invention is not limited to this. It is also possible to apply when manufacturing by the VB method.

[0064]

According to the present invention, a cylindrical crucible with a bottom having an inverted conical diameter increasing portion on the lower end side and a seed crystal installation portion at the center of the bottom of the diameter increasing portion is provided. A seed crystal is set in the seed crystal setting part of the crucible, a raw material of a compound semiconductor and a sealing agent are charged into the crucible, and the crucible is sealed in an airtight container. The raw material and the sealant are placed in and heated and melted by heating means,
When growing the compound semiconductor single crystal by gradually cooling the obtained raw material melt from the lower side and solidifying it from the seed crystal upward, the crystal growth rate in the diameter-increased portion of the crucible was increased by 20 mm. / Hr or more, so that twins can be effectively prevented from being generated in the diameter-increased portion of the crystal.
A compound semiconductor single crystal can be obtained with a high yield,
In particular, there is an effect that it is possible to efficiently manufacture a compound semiconductor single crystal, such as InP, which easily causes twinning at a low cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a crucible and peripheral devices applied to a method for producing a compound semiconductor single crystal according to the present invention.

FIG. 2 is a schematic explanatory view showing a diameter increasing portion of a crucible.

FIG. 3 is a schematic view of a crystal growth furnace applied when the present invention is applied to a VGF method.

[Explanation of symbols]

1 crucible 2 or crystal growth section 3 material (InP polycrystal) 4 sealant (B ₂ O ₃₎ 5 inner container 6 crucible susceptor 7 Thermocouple 8 Lid S seed A rose diameter 10 high pressure vessel 11 the cylindrical multi-stage graphite Heater 12 Lower shaft 13 Hot zone 14 Hot zone lid

Claims (3)

[Claims] 1. A crucible having a bottomed cylindrical shape having an inverted conical diameter increasing portion on a lower end side and a seed crystal installation portion at the center of the bottom of the diameter increasing portion. A seed crystal is placed in the part, a compound semiconductor raw material and a sealing agent are charged into the crucible, and the crucible is sealed in an airtight container. When a single crystal of a compound semiconductor is grown by heating and melting the raw material and the encapsulant by a heating means and gradually cooling the obtained raw material melt from the lower side and solidifying the raw material melt upward from the seed crystal. The crystal growth rate at the diameter-increased portion of the crucible is 2
A method for producing a compound semiconductor single crystal, wherein the crystal is grown at 0 mm / hr or more. 2. The compound according to claim 1, wherein the inverted conical diameter-increased portion of the crucible has a predetermined inclination angle of 40 ° or more and less than 90 ° with respect to a normal line at the bottom center. A method for manufacturing a semiconductor single crystal. 3. A temperature gradient in a crystal growth direction of at least the diameter-increased portion of the crucible during crystal growth is 1 to 10 ° C.
3. The method for producing a compound semiconductor single crystal according to claim 1, wherein the control is performed so as to obtain a single crystal.